Implement CENG-WP-0002: package distribution and publish readiness

Resolve ADR-0002 in umbrella, add install docs, contract sync runbook,
publishing checklist, and package files whitelist.

package.json

@@ -9,6 +9,12 @@
   "engines": {
     "node": ">=20.10.0"
   },
+  "files": [
+    "src",
+    "wiki",
+    "README.md",
+    "LICENSE"
+  ],
   "exports": {
     ".": "./src/engine/index.ts",
     "./shared": "./src/shared/index.ts"